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Setup:

Our house is a two-story built in 2011. We have zoned HVAC off a single unit with electronic dampers. The upstairs has three bedrooms and two bathrooms. The master bedroom is the only room that has a vaulted ceiling. The attic spans over all of the other upstairs rooms except for the master bedroom. The vents in all of the rooms are wide open and not blocked. The system's air filter is brand new. We have blackout curtains over the master bedroom window that are closed essentially all of the time.

Issue:

When the upstairs thermostat (Nest 3rd Gen. in the hallway) calls for AC, the master bedroom cools off much slower than the rest of the rooms. We installed a Nest Temperature Sensor in the master bedroom so that the master bedroom stays the desired temperature, but this results in all of the other rooms being much colder than desired (typically 5-8 degrees colder than what the thermostat is set to).

Question:

Are there any solutions that we can deploy to balance the cooling in the master bedroom better with the rest of the rooms? Our HVAC guy just said it was because the master bedroom does not have the attic to assist with insulation, but I am not willing to accept that there is no solution.

Thanks!

  • make more air flow where it's too hot, less air flow where it's too cold, no tech required... – dandavis Jul 20 '18 at 17:23
  • How much R-value is there between the master bedroom ceiling and the actual roof? This sounds like a situation where you need to rethink where the air and thermal barrier planes over your head are... – ThreePhaseEel Jul 20 '18 at 22:17
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I would adjust the dampers so the ones in the smaller rooms are not fully open this will put more flow to the larger room. Things to think about that can reduce flow to a room is the bottom of the door jamb tight to the carpet or floor this can act like a damper once the room is pressurized the flow will be reduced with the damper open. If this is the case trim the bottom door, I state this because the return air duct is usually in a common area for each floor. Your HVAC guy is correct a larger room with less dead air space (attic above) will take longer to cool, BUT a properly size duct(s) and damper control they can be setup to cool at similar rates.

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    +1 for recognizing a room can get pressurized without some air “relief” capabilities, like return air duct, undercut door, etc. – Lee Sam Jul 20 '18 at 17:34
  • Ok, thanks. Just to confirm (I'm an HVAC newbie), when you say "damper" are you referring to the vents themselves, or actual dampers in the ducts? Obviously adjusting the vents themselves to be partially closed would be really easy, but my HVAC guy and a few articles I've found online said that that is hard on the AC fan? – Collin Barrett Jul 20 '18 at 17:38
  • I'll definitely check the carpet/door, though. I think that may be spot on. I think there is essentially no gap, and I don't think there is a return in the master bedroom itself. Now, to figure out how to trim a door... (not a handyman and have no saws, lol.) – Collin Barrett Jul 20 '18 at 17:39
  • Test the effect of cutting off the bottoms of doors by leaving the doors under test open an inch or half an inch. Get door wedges or use makeshift door stops to hold the door slightly open. – Jim Stewart Jul 21 '18 at 1:11

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